(Problem 14.2-6) Threshold Population Difference for an Ar+
-Ion Laser.
An Ar+
-ion laser has a 1 m-long resonator with 98% and 100% mirror reflectances. Other loss mechanisms are negligible. The atomic transition has a central wavelength = 515 nm, spontaneous lifetime = 10 ns, and linewidth Δ = 3 pm (note the unit!). The lower energy level has a very short lifetime, and thus, nearly zero population. The diameter of the oscillating mode is 1 mm. Determine (a) the photon lifetime and (b) the threshold population difference for laser action.